Experimental
research:
It is the research in which the
researcher manipulates the independent variable and is interested in showing
cause and effect.
The purpose of experimental research is
to determine cause-and-effect relationships. The experimental research method
enables us to identify causal relationships because it allows us to observe, under control conditions, the
effects of systematically changing one or more variables.
Non-experimental
research:
In non-experimental research, there is
no manipulation of an independent variable. There is also no random assignment
to groups by the researcher.
As a result of these two deficiencies (no
manipulation and no random assignment), evidence gathered in support of
cause-and-effect relationships in non-experimental research is severely limited
and much weaker that evidence gathered in experimental research.
If the researcher wants to study cause
and effect, he/she should try to conduct an experiment, but sometimes this is
not feasible. When important causal research questions need to be answered and
an experiment can’t be done, research must still be conducted. In research, we
try to do the best we can.
For example, during the 1960s,
extensive research linking cigarette smoking to lung cancer was conducted.
Experimental research with humans was not possible because it would have been
unethical. Therefore, in additional to experimental research with laboratory
animals, medical researchers relied on non-experimental research methods for
their extensive study of humans.
Descriptive
Research:
A descriptive study describes and
interprets what is. It is concerned with conditions or relationships that
exist, opinions that are held, processes that are going on, effects that are
evident, or trends that are developing.
Descriptive study deals with the relationships
between variables, the testing of hypotheses, and the development of
generalizations, principles, or theories that have universal validity.
Descriptive study is sometimes divided
into correlational research, causal-comparative research, and other descriptive
research that is neither correlational nor designed to find out causation but describes
existing conditions.
In carrying out a descriptive research
project, in contrast to an experiment, the
researcher does not manipulate the variable, decide who receives the
treatment, or arrange for events to happen. Descriptive research also involves
events that have already taken place and may be related to a present condition.
Descriptive research seeks to find
answers to questions through the analysis of variable relationships. What
factors seem to be associated with certain occurrences, outcomes, conditions,
or types of behaviors?
Because it is often impracticable or
unethical to arrange occurrences, an analysis of past events or of already
existing conditions may be the only feasible way to study causation. This type
of research is usually referred to as ex-post facto or causal-comparative
research or, when correlational analyses are used, as correlational research.
Causal-comparative
research:
In causal-comparative research, the
researcher studies the relationship between one or more categorical independent
variables and one or more quantitative dependent variables.
Because independent variable is
categorical (that is males vs females, parents vs non-parents, or public school
teachers vs private school teachers), the different group’s average scores on a
dependent variable are compared to determine whether a relationship is present
between the independent variable and dependent variable.
Despite the presence of the word causal
included in the term causal-comparative research, one must keep in mind that
causal-comparative research is a non-experimental research method, which means
that there is no manipulation of an independent variable by a researcher.
Because of lack of manipulation and
weaker techniques of controlling for extraneous variables, it is much more
difficult to make statements about cause and effect in causal-comparative
research than in experimental research.
